Strong experimental evidence in animals has been accumulated by our group in support of the hypothesis that nutritional insults occurring during the critical period of dental tissue formation predispose to caries, enamel defects and changes in enamel composition immune response and salivary flow and composition. We have also carried out two preliminary investigations among Guatemalan (retrospective) and Peruvian children (cross-sectional) that demonstrated a positive correlation between undernutrition and increased caries. A careful examination of the dental literature provides epidemiological evidence from human studies which supports our hypothesis. Caries incidence in permanent molars correlates with tooth morphology and time of exposure to the oral environment; incidence in 1st molars is therefore higher than in 2nd molars. In primary teeth this is just the opposite; 2nd molars have a much higher caries incidence that 1st molars, an intriguing finding that has not been satisfactorily explained by morphological differences between these teeth. 1st primary molars are formed form 5 mo. in utero to 5 mo. post-partum while 2nd primary molars are developed from 6 mo. in utero to 11 mo. post-partum. The incidence of malnutrition and infection in infants rises dramatically after the 5th mo. of age (weaning). In agreement with our proposed hypothesis it is the 2nd primary molars, which are still in the period of enamel formation when malnutrition and infection are most frequent, that show the highest incidence of caries. The lack of a well-defined model has largely prevented the experimental testing of the effect of nutrition on dental growth and caries susceptibility in a human population. We have developed a model that will directly test the validity of our hypothesis. It is based on the prediction that nutritional insults imposed at selected developmental stages since late-gestation to 10 months of age will result in specific differences in development and caries incidence of individual teeth. We specifically propose to carry out a longitudinal study in children from a high-caries incidence area where malnutrition is also prevalent. A complete nutritional assessment of the subjects will be made using anthropometric, dietary and biochemical parameters. An evaluation of tooth eruption and size, enamel composition and defects, caries activity, saliva flow and composition (microbial and immunological parameters), mandible growth, arch size and occlusion will be made and correlated with nutritional status during defined periods of dental tissue formation Sugar and fluoride intake will also be assessed.